Public libraries frequently have small rooms you can use for free on a first-come first-served basis, and plenty of carrels in the stacks.

Whenever I need to meet someone to discuss something in-person (for my biz, not for my writing), I'll usually offer to meet them in public somewhere that serves food and drink.

If you need office space to impress someone as being legit, you might look into an office-sharing company for a minimal monthly $$$. But even though I have plenty of space my back pocket that I could potentially convert into office space for my biz, I'm not interested in paying for electric/water/sewer/trash/gas/phone/internet/cable/whatever every month. My phone, my computer, and a filing cabinet are good enough for my main biz... and my writing requires even less.

I have other things to do with $3-$6k/year-- or whatever prices are in southern California.